1. Field of the Invention
The present invention relates to a format of address information which is used for correctly recording or reproducing information at a prescribed position in an information recording medium, and a technology for recording or reproducing information in accordance with the address information format.
2. Description of the Related Art
Recently, research and development of high density optical discs has been actively conducted. Currently, for example, Blu-ray Disc (BD) has been proposed and put into practice, and is used for recording digital broadcast or the like. Optical discs are now establishing their position as an important information medium. For further increasing the density, research and development for providing a higher recording density than that of BD to expand the recording capacity is now being conducted.
FIG. 13 shows an example of a format of track addresses pre-recorded on a track of a conventional optical disc. This is not a track address format of a BD mentioned above.
The track is divided into blocks by a data recording unit of 64 kB (kilobytes), and the blocks are sequentially assigned block address values. Each block is divided into sub blocks each having a prescribed length. Six sub blocks form one block. The sub blocks are assigned sub block numbers of 0 through 5 from the first sub block.
Digital information of 21 bits in total including 18-bit digital information representing the block addresses and 3-bit digital information representing the sub block number is pre-recorded on each sub block of the track. An optical disc apparatus for performing recording to or reproduction from the conventional optical disc reproduces the 21-bit digital information for each sub block and searches for a target block while following the block addresses and the sub block numbers, and thus can perform data recording to or data reproduction from the target block.
FIG. 14 shows the relationship between a range of addresses which can be represented by the address format of the conventional optical disc and the data recording capacity.
In the conventional optical disc, as shown in FIG. 13, 18-bit digital information is assigned as a block address. For example, in the case where the recording capacity is 15 gigabytes (GB), the block address values are represented by the numerals of 00000 through 39387 (hexadecimal notation).
FIG. 15 shows an address format of data addresses to be added to data at the time of data recording to a conventional optical disc.
Data is recorded as being divided into blocks each having 64 kilobytes (kB). The size of the data block is the same as the size of the block obtained by dividing the track. Each block is further divided into sectors each having 2 kB. As a result, one block includes 32 sectors.
Two consecutive sectors are managed as one data unit. At the start of each data unit, 4-byte (32-bit) data address information is inserted and recorded on a track. As shown in FIG. 15, the conventional data address information includes, from the least significant bit side, a 5-bit sector number, an 18-bit block address value, and 9-bit control information. Thus, the conventional data address information has 32 bits in total. The control information is used for describing layer information in the case where there are a plurality of recording layers.
The data address is provided at the start of each data unit. Therefore, the sector number assigned to the least significant 5 bits is always even-numbered. This means that the value of the least significant bit is always 0.
The 18-bit block address value is the same as the value of the block address pre-recorded on the track. A block address value of the target block in which data is to be recorded is assigned as the 18-bit block address value (see, for example, Japanese Laid-Open Patent Publication No. 2002-352521).
According to the address format of the conventional optical disc, the digital information assigned as a block address is of 18 bits. As shown in FIG. 14, only values of up to 3FFFF at the maximum can be represented as the block address. This means that the recording area is expandable only to 16.7 GB. This is not usable for an optical disc having a capacity of more than 16.7 GB so does not satisfy the demand for a significant expansion of the recording capacity.
In order to expand the recording capacity, digital information representing a block address to be recorded on the track could be expanded to be of equal to or more than 19 bits. However, the address format of such information is totally different from that of the conventional optical disc and is not compatible thereto. This requires installation of hardware (optical disc apparatus, optical disc production apparatus) corresponding to the new address format and significantly increases the cost.
Similarly, regarding the data address, the digital information representing a block address is of 18 bits. Therefore, the block addresses only in the range from 00000 through 3FFFF can be represented, and the capacity cannot be further expanded.